Without limiting the scope of the present inventions, their background is described with reference to setting tools, downhole force generators and downhole power units and improvements thereto. It is typical in hydrocarbon wells to “set” or actuate downhole tools, such as packers, bridge plugs, high-expansion gauge hangers, straddles, wellhead plugs, cement retainers, through-tubing plugs, etc. Additionally, some of these tools are later “unset” for retrieval. Setting tools are run-in, and in some cases retrieved, using various conveyance methods such as a wireline, slickline, or coiled tubing. The generic name for the running tool which provides the large setting forces required is a setting tool.
Several types of setting tool and downhole force generators are known in the art, including those operated mechanically, electrically, chemically, explosively, hydraulically, electro-mechanically, etc. One type of DFG uses electro-mechanical power, where the DFG converts electrical power, typically provided by a battery unit, into mechanical movement, typically rotary or longitudinal movement of a shaft or power rod. One such setting tool is the DPU (trade name) Downhole Power Unit available from Halliburton Energy Services, Inc.
Additionally, industry standard setting tools, for example, the Baker E4 or Baker 20 setting tool and the Halliburton “Shorty,” operate utilizing a force generated by rapidly burning chemicals, typically in a pyrotechnic charge, to create a high-pressure gas. Such explosive tools are referred to generically as “pyrotechnic” setting tools or force generators. These tools create and contain high pressure gas by igniting a pyrotechnic charge in a closed chamber. The pyrotechnic charge is initiated by electrical current supplied from the surface down an electric cable or from batteries carried downhole with the setting tool and used in conjunction with associated pre-programmed timers, electronics package, etc. The chamber containing the high pressure gas features a floating hydraulic piston with an oil filled chamber below. The hydraulic oil is pressured by the expanding gas, providing hydraulic power which performs the setting task. Disadvantages to such pyrotechnic setting tools include the necessity of transporting a gas-pressured container to the surface after use and releasing the pressure in a controlled and safe manner Such venting is hazardous and conducted under strictly controlled conditions. Further, extensive and costly regulations require special shipping and handling of the pyrotechnic tools by trained personnel, storage on licensed premises, third party notification when shipping, inspections by official personnel, and routine inspections.
Hydrostatic setting tools convert ambient hydrostatic pressure in a wellbore into hydraulic force to set the downhole tool. The setting tool is equipped with a series of pistons which each have atmospheric pressure on both sides of the piston. The piston series provides motive force. When a valve is opened (by signal or timer) well pressure acts on one side of the pistons causing a pressure imbalance. Bottom hole pressures are typically too small produce sufficient hydraulic power to set a tool, so the force-multiplier pistons generate the pressures needed. Typically, a 1 to 5 multiplier may be required. Such tools can be unwieldy due to the required length necessary for the series of pistons and performance is only marginal in certain circumstances.
Hydraulic setting tools operate based on operator-increased pressure in the tool string. Typically a mandrel is connected to a work string, a stationary piston connected to the mandrel and dividing an interior chamber into two hydraulic chambers, and a hydraulic cylinder is slidingly mounted on the mandrel. An inlet port allows fluid into the bottom hydraulic chamber, which in turn urges the cylinder away from the stationary piston. As the cylinder moves downward, fluid flows out of the top hydraulic chamber via an outlet port. The movement of the cylinder is used to actuate or set other tools. Hydraulic setting tools can be damaged by hostile environments. Extreme hydrostatic pressure and imbalances between interior and exterior pressures can impair subsequent operation by deforming tool parts.
Disclosure relating to downhole force generators, their operation and construction can be found in the following, which are each incorporated herein for all purposes: U.S. Pat. No. 7,051,810 to Clemens, filed Sep. 15, 2003; U.S. Pat. No. 7,367,397 to Clemens, filed Jan. 5, 2006; U.S. Pat. No. 7,467,661 to Gordon, filed Jun. 1, 2006; U.S. Pat. No. 7,000,705 to Baker, filed Sep. 3, 2003; U.S. Pat. No. 7,891,432 to Assal, filed Feb. 26, 2008; U.S. Patent Application Publication No. 2011/0168403 to Patel, filed Jan. 7, 2011; U.S. Patent Application Publication Nos. 2011/0073328 to Clemens, filed Sep. 23, 2010; 2011/0073329 to Clemens, filed Sep. 23, 2010; 2011/0073310 to Clemens, filed Sep. 23, 2010; and International Application No. PCT/US2012/51545, to Halliburton Energy Services, Inc., filed Aug. 20, 2012.
It is an object of the invention then, to provide a pressure-actuated setting tool with a self-contained motive force generator. It is a further object of this invention to provide a setting tool which is not subject to the regulations and restrictions of typical pyrotechnic setting tools. It is a further object of the invention to provide a setting tool with regulated setting speeds. It is a further object of this invention to provide a setting tool which is force-balanced. It is a further object of this invention to provide a setting tool of reasonable length. Other objects and benefits will be apparent to those of skill in the art.